Genomics of consumer traits in chapatti quality

Abstract

Wheat is a complex domesticated cereal crop, used by humans throughout the globe. Wheat is consumed in India and Pakistan in the form of chapatti. Around 90% of the wheat produced in India is consumed as chapatti, while the remaining 10% is used for bread, biscuits and other products. Despite such large consumption of the product, understanding of the physico-chemical and molecular basis of chapatti quality is poor. Chapatti quality testing has been mainly based on subjective scoring. A texture analyser (Kieffer rig) used for dough rheology testing, was evaluated for use in testing baked chapatti extensibility or resistance to extension. Chapatti and bread quality analysis for nine wheat genotypes was used to explore the relationships between the quality requirements for these two end products. Chapatti quality analysis was performed on 34 diverse wheat genotypes to determine the relationships between chapatti scores and the physico-chemical properties of the wheat. RNA seq analysis was used to determine the relationship between chapatti quality and gene expression in the wheat at 14 DPA.Phenotypic analysis of bread and chapatti revealed differing wheat quality requirements for chapatti and bread quality. The Kieffer rig chapatti extension measurement method was found to be effective in the objective assessment of chapatti quality. The study revealed the importance of several physico-chemical parameters for chapatti quality. Wheat hardness controls milling, chapatti pliability and overall score. A lower protein (9-13%) is desirable in chapatti with lower gluten imparting lower dough strength. The sedimentation value did not correlate with the overall chapatti score, whereas it helped in predicting the rheological behaviour of the dough. An extensograph and a farinograph were used for estimation of rheological performance and revealed that lower dough strength offers better end product quality in chapatti production. The extensibility of the dough did not correlate with the chapatti quality.The transcriptomic data analysis revealed HMW GS Dx5 + Dy10, LMW GS and a-gliadins genes were differentially expressed in good and poor chapatti quality wheat, contributing to chapatti quality. Transcript analysis also showed that the wheat breadmaking gene was highly down-regulated in genotypes with good chapatti quality. Overall, the genetic requirements of the wheat for bread and those for chapatti quality differed widely.nThe study found large variations in the quality requirements of bread and chapatti, making it difficult to breed wheat for good bread and chapatti simultaneously. Much work needs to be done for understanding the effect of quantitative expression of candidate genes on chapatti and bread quality to help match wheat varieties to chapatti and bread industryn needs. The identification of candidate genes for chapatti quality will also support the development of marker based screening of wheat for chapatti quality as a majorndevelopment in Indian wheat breeding.